Issue #8 Implement --split-chapters

This only works when we're in series mode.

Example output:

> $GOPATH/bin/gomkv --series --prefix C --split-chapters 5 --episode 6
HandBrakeCLI -Z "High Profile" -i /mnt/scratch/C/title00.mkv -t1 -c1-5 -a1 -E copy:ac3 -s 1,2 -o /mnt/scratch/C/C_S1E06.mkv
HandBrakeCLI -Z "High Profile" -i /mnt/scratch/C/title00.mkv -t1 -c6-10 -a1 -E copy:ac3 -s 1,2 -o /mnt/scratch/C/C_S1E07.mkv
HandBrakeCLI -Z "High Profile" -i /mnt/scratch/C/title00.mkv -t1 -c11-15 -a1 -E copy:ac3 -s 1,2 -o /mnt/scratch/C/C_S1E08.mkv
HandBrakeCLI -Z "High Profile" -i /mnt/scratch/C/title00.mkv -t1 -c16-20 -a1 -E copy:ac3 -s 1,2 -o /mnt/scratch/C/C_S1E09.mkv
HandBrakeCLI -Z "High Profile" -i /mnt/scratch/C/title00.mkv -t1 -c21-25 -a1 -E copy:ac3 -s 1,2 -o /mnt/scratch/C/C_S1E10.mkv

Splits a single video file into chapter stops so you can watch each
episode individually

- Introduce GomkvSession to hold changing values
- Add GomkvConfig.SplitFileEvery
- Add session object to API for FormatCLIOutput
- Rename FormatCLIOutput to FormatCLIOutputEntry
- Make FormatCLIOutput responsible for chapter splitting
- Change FormatCLIOutput to return an Array of Strings so the output can
  be tested
- Update Encode to add Chapter Start and Stop values when enabled
- Update unit tests for new API
- Ignores Chapter stops if there aren't enough chapters in file
- Test new GomkvSession object for regular Episodic
- Test Chapter Splitting
- Go fmt
Update README with new example